1. Field of Technology
This disclosure relates generally to liquid and gas ultrasonic flow meters. More particularly, it relates to an apparatus and system for protecting cables extending from ultrasonic flow meters.
2. Background Information
Hydrocarbons, in both liquid and gas phases, are transported from place to place via pipelines. It is desirable to know with accuracy the amount of fluid flowing in the stream, and particular accuracy is demanded when the fluid is changing hands, or during “custody transfer.” Even where custody transfer is not taking place, measurement accuracy is desirable, and in these situations, ultrasonic flow meters are commonly used.
An ultrasonic flow meter typically includes two or more transducer assemblies, each secured inside of a dedicated port in the body of the flow meter. The body of the flow meter may also be referred to as a spool piece. To seal the transported fluid within the flow meter, a connector is secured over the exterior end of each transducer port in the spool piece. Thus, the spool piece and end connectors create a sealed housing and pressure boundary that contains the fluid that is flowing through the meter.
To measure fluid flow through the meter, a pair of transducer assemblies is positioned such that the piezoelectric elements of the transducers are adjacent to the inner surface of the spool piece, and such that each transducer of the pair faces the other of the pair that is positioned on opposite sides of the fluid-carrying bore of the spool piece. The transducer assemblies transmit and receive electric signals back-and-forth across the fluid stream.
Each transducer assembly is coupled to a cable that extends through the end connector to the exterior of the spool piece, and to a remote location, typically an electronics enclosure mounted on or adjacent to the spool piece. The electric signals created by the piezoelectric element of the particular transducer assembly is carried by the cable to an acquisition circuit board housed within the electronics enclosure, where the signal may be processed and subsequently used to determine the fluid flow rate through the meter.
Typically, the transducer cables are run to the electronics enclosure along the outer surface of the spool piece, where they remain constantly exposed to weather and sunlight, which can degrade the cables' insulation. Left exposed, the cables are also susceptible to being tampered with and to becoming damaged by causes such as falling debris, livestock contacting or eating the cables, and vandals. Further, left unprotected, the cables and transducers are exposed to possible damage during shipping and installation. Consequently, it is common to employ robust and thus relatively expensive such cables in an attempt to resist damage and degradation.
Some attempts have been made to manufacture meter bodies having internal cable passageways that are formed in the walls of the meter body to at least partially cover the cables and to provide some degree of protection. In some such products, the ends of the transducer assemblies and portions of the cables are nevertheless still exposed and thus susceptible to damage. Further, although the cables may be partially covered, access to the transducer assemblies in such products is not prevented, such that the transducer assemblies may be tampered with, with no indication that such tampering has taken place. Tampering with transducers and cable connections may disable the meter completely, or alter the meter's performance in accurately measuring fluid flow.
Accordingly, there remains a need in the art for a flow meter in which transducers and transducer cables are protected from damage, but where the cables and transducers are readily accessible so service can be provided when required.